My drive was also purchased from an online source (retail version - not OEM) and failed to read movie disks straight out of the box - it was the first thing I tried to do with it. As the paperwork in the box said the drive was gauranteed by Plextor for 2 yrs I went to the Plextor website and completed their RMA Request Form.
I got a reply with an RMA number the next day with instructions how to phone their DHL courier who came to my door and collected the drive at no cost to me.
The next day I got an e-mail saying my replacement drive has been shipped next day delivery. (should be here tomorrow (Monday)
Assuming all things being equal and the new drive works OK then I'm more than happy and cannot fault the service from Plextor. I wish all retailers were that good about faulty kit. I'll post the result with the new drive out of interest.
How was your new drive - did it work OK?